The invention relates to a digital placard suitable for mounting on airplanes, wherein the placard is made using a thermal digital printer and covered with a protective coating.
Aviation places significant stress on graphic arts materials such as placards. An aircraft placard is a text and/or graphic decal that communicates information, corporate image and aircraft identification to people who work with and support the aircraft. A placard placed on the exterior of an airplane will be subjected to extremes of heat and cold, dryness and wetness, pressure variations, and also be exposed to significant amounts of ultraviolet light when the airplane is at high elevations. As a result, the maintenance and replacement of aircraft exterior markings represents a considerable expenditure of time and money.
A typical method for producing placards or transfer graphics with sealed edges is discussed in U.S. Pat. No. 4,759,982 to Jennsen et al. U.S. Pat. No. 4,759,982 pertains to a process for preparing a transfer graphic article having a protective clear coat in precise registration such that the graphic article has rounded and sealed edges. The edges of the underlying adhesive are sealed by the clear coat such that improved solvent resistance is achieved. Jennsen et al. fails to disclose how the graphic aspect of the article is generated or that the shape of the cut defining the shape of the article. Example 4 of Jennsen et. al discusses the use of an aliphatic urethane acrylate in a clear coat formulation, but when combined with wet ink printing and a 3 minute drying time, this would not be a rapid process.
The application of thermal printing techniques to the produce aircraft exterior markings and placards has the potential to provide a superior product at low cost. However, the extreme conditions associated with aviation applications represent significant problems which must be overcome in order for this technology to be utilized.
Thermal printers are used to print on a variety of non-paper substrates (films). The printer is somewhat similar to a typewriter. A selected colored ribbon, which can be 12 inches wide, is loaded into the printer. The ribbon can be a plastic sheet with a coating of pigment applied to one side. The printer is loaded with the selected substrate for the application. A print head is commanded by a computer system. The print head is a pixeled thermal head. The thermal pixels make contact with the ribbon, and the heat causes the resin to release from the ribbon to the substrate in the form of the computer commanded graphic.
Typical thermal ribbon printing technology is discussed in U.S. Pat. No. 5,803,627 to Paranjpe. U.S. Pat. No. 5,803,627 discusses the transfer of ink caused by electrical pulse which are transmitted to a thermal head. The thermal energy brings about the transfer of the resin onto the substrate. However this technology requires a sublimation dye or an encapsulated radiation resistant dye. These dyes would be expected to have poor stability when exposed to the rigorous conditions of aviation applications.
There are many disadvantages associated with the currently used silk screen processes used to manufacture aircraft placards. Silk screening is slow and labor intensive. As a result, silk screen placards are costly to produce. Solvents such as acetone are used during silk screening, and the shop personnel can be exposed to these solvents. In contrast, thermal transfer uses no solvents. Thermal transfer also uses computer technology to generate and transfer the image, significantly reducing initial set-up time for each color. As a result, thermal transfer technology promises to produce a low cost aircraft placard with reduced environmental hazards.
The invention, in part, pertains to a digital placard made using a thermal digital printer. After printing, the placard is coated with a protective layer or ink. The protective layer is cured using ultraviolet light. The protective layer or ink can contain an adhesion promoter such as polymeric hexamethylene diisocyanate.
The invention, in part, pertains to a thermally digital printed placard coated with an ink containing 45-70% acrylates, 15-30% resin mixtures, 0-35% pigments, 0-2% alkylamine such as methyldiethanolamine, up to 5% photoinitiators, and up to 2% antifoam. The ink is cured using ultraviolet light. The ink can also optionally contain an adhesion promoter such as polymeric hexamethylene diisocyanate.
The invention, in part, pertains to a digital placard to be applied to an aircraft. The digital placard is made using a thermal digital printer. After printing the placard is coated with a protective ink using a silk screen process. The ink is instantly cured when it is exposed to ultraviolet light. The silk screen ink can contain an adhesion promoter such as polymeric hexamethylene diisocyanate. The digital placard is applied to the airplane, and the edges are sealed using an edge sealer.